Enriched mantle

Oceanic mantle Young magmatic rocks record the isotopic composition of their source directly. 

The isotopic anomaly was expressed by Hart (1984) in terms of A 7/4 and A 8/4, defined as the vertical deviation from the reference line so that for a given dau-set (DS)  

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Rabinowicz M, Ceuleneer G, Monnereau M, Rosemberg C (1990) Three-dimensional models of mantle flow across a low-viscosity zone implications for hotspot dynamics. Earth Planet Sci Lett 99 170-184 Reid MR(1995) Processes of mantle enrichment and magmatic differentiation in the eastern Snake River Plain Th isotope evidence. Earth Planet Sci Lett, 131 239-254 Reid MR, Ramos FC (1996) Chemical dynamics of enriched mantle in the southwestern United States Thorium isotope evidence. Earth Planet Sci Lett, 138 67-81. 

In the 143Nd/l44Nd vs 87Sr/86Sr plot, draw the mixing triangle at the 20 percent mesh size for a mixture of three mantle components, the depleted mantle (DM), the enriched mantle I (EM I) and the enriched mantle II (EM II). The isotopic ratios and relative concentrations of each component are listed in Table 1.10. 

Castorina F, Stoppa F, Cundari A, Barbieri M (2000) An enriched mantle source for Italy s melilitite-carbonatite association as inferred by its Nd-Sr isotope signature. Mineral Mag 64 625-639... 

Hart SR, Hauri EH, Oschmann LA, Whitehead JA (1992) Mantle plumes and entrainment isotopic evidence. Science 256 517-520 Hawkesworth CJ, Vollmer R (1979) Crustal contamination vs. enriched mantle 143Nd/144Nd and 87Sr/86Sr evidence from the Italian volcanics. Contrib Mineral Petrol 69 151-165... 

Nakai S, Wakita H, Nuccio M, Italiano F (1997) MORB-type neon in an enriched mantle beneath Etna, Sicily. Earth Planet Sci Lett 153 57-66 Nappi G, Renzulli A, Santi P (1987) An evolutionary model for the Paleo-Bolsena and Bolsena Volcanic Complexes a structural and petrographic study. Per Mineral 56 241-267... 

Workman R. K., Hart S. R., Blusztajn J., Jackson M., Kurz M., and Staudigel H. (2003) Enriched mantle II. A new view from the Samoan hotspot. Geochem. Geophys. Geosys. (submitted). 

Kempton P. D. (1987) Mineralogic and geochemical evidence for differing styles of metasomatism in spinel Iherzolite xenoUths enriched mantle source regions of basalts In Mantle Metasomatism (eds. M. A. Menzies and C. J. Hawkesworth). Academic Press, London, UK, pp. 45-89. 

Menzies M. and Murthy V. R. (1980a) Enriched mantle Nd and Sr isotopes in diopsides from kimberlite nodules. Nature 283, 634-636. 

Rodgers N. W., De Mulder M., and Hawkesworth C. J. (1992) An enriched mantle source for potassic basanites evidence from Karisimbi volcano, Virunga volcanic province, Rwanda. Contrib. Mineral. Petrol. Ill, 543-556. 

Dixon et al. (2002) take this approach one step further, and use new data on water contents, trace element and isotope geochemistry of Atlantic basalts to argue that mantle endmember reservoirs or components, previously defined on the basis of their isotope geochemistry, have different water contents. They propose that depleted MORE mantle (DMM) has 100 ppm H2O, FOZO ( focus zone component of Hart et al., 1992) has 750 ppm H2O, and enriched mantle (EM) has approximately half the H2O concentration as FOZO. 

Reid M. R. and Ramos R. (1996) Chemical dynamics of enriched mantle in the southwestern United States thorium isotope evidence. Earth Planet. Sci. Lett. 138, 239-254. 

Another very active area of recent research is the identification of several different source components in primary arc basalts, including (i) fluids derived by dehydration of subducting metabasalt, (ii) fluids derived by dehydration of subducting metasediment, (iii) partial melts of subducting basalt, (iv) partial melts of subducting sediment, (v) fertile mantle peridotite similar to the MORE source, (vi) mantle peridotite depleted by melt extraction beneath a mid-ocean ridge and/or a back-arc basin, and (vii) enriched mantle similar to... 

Tatsumi Y. (2000) Continental crust formation by delamination in subduction zones and complementary accumulation of the enriched mantle I component in the mantle. Geochem. Geophys. Geosys. (G-cubed) 1, 1-17. 

Antonini, P., Picirillo, E., Petrini, R., Civette, L., D Antonio, M. Orsi, G. 1999. Enriched mantle - Dupal signature in the genesis of the Jurassic Ferrar tholeiites from Prince Albert Mountains, Victoria Land, Antarctica. Contributions to Mineralogy and Petrology, 136, 1-19. 

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